Doubt in LIKE.

Question

Hi,
I have a doubt in like operator.
i have created a table and inserted few records by using the following sql statements.
CREATE TABLE james_sample1 (a VARCHAR2(20));
INSERT INTO james_sample1 VALUES(12);
INSERT INTO james_sample1 VALUES(123);
INSERT INTO james_sample1 VALUES(1234);
INSERT INTO james_sample1 VALUES(12345);
INSERT INTO james_sample1 VALUES(123456);
and i try the following query,
SELECT * FROM james_sample1 WHERE a LIKE '%_%';
and the above query returns all the records. but none of the columns has '_' in it.
can any body tell me why it behaves like this?
Thanks,
James

Answer 1

Hi James,
By SQL, the character '_' underscore with 'LIKE' means "any character, specific length" (as in the opposite of %, which means "any character, no specific length").
So, what you were asking is: give me the values that consist of any character of no specific length, followed by any character which is exactly 1 position long and then followed by any character(s) again. No wonder that all values come up...
Usually, you would use _ like this: where view_name like 'myview_'1, which would give back myviewA1, myviewB1, etc. But not myviewCCC1
Sometimes, the _ can be a problem, for example when you want all views with a name that begins with TEST_, but not TEST1. Then, use substr(view_name,1,3) = 'TEST_', because _ only works like a wildcard with like.
Regards,
Sabine
Regards,
Sabine